Apparatus for and method of graphical recording with simultaneous charging and inking

ABSTRACT

In a graphical recording apparatus, a substantial and continuous flow of marking liquid moves between a discharge port and a vacuum port in communication with a record receiving medium. In both electrographic printing and ink pen embodiments, the vacuum port comprises a vacuum chamber surrounding the discharge port. The charge despositing styli in the electrographic printing embodiment are also surrounded by the vacuum chamber.

United States Patent 1 1 Weiss et a1.

[ Feb. 19, 1974 APPARATUS FOR AND METHOD OF GRAPHICAL RECORDING WITH SIMULTANEOUS CHARGING AND INKING Inventors: Edward L. Weiss, Quakertown;

Barry A. Bell, Glenside, both of Pa.

Assignee: Leeds & Northrup Company, North Wales, Pa.

Filed: July 10, 1972 Appl. No.: 270,327

US. Cl. 346/74 ES, 118/410 Int. Cl. G0ld 15/06, G03g 9/04 Field of Search178/96, 91; 346/140, 75, 74 ES;

' References Cited- UNITED STATES PATENTS 9/1967 Lewis 118/410 3,371,651 3/1968 Johnson 1l8/DlG. 23 3,302,564 2/1967 Wilford... 118/410 3,540,409 11/1970 Lloyd 346/74 ES Primary ExaminerVincent P. Canney Assistant Examiner.lay P. Lucas Attorney, Agent, or FirmWoodcock, Washburn, Kurtz & Macklewicz [5 7 ABSTRACT In a graphical recording apparatus, a substantial and continuous flow of marking liquid moves between a discharge port and a vacuum port in communication with a record receiving medium. In both electrographic printing and ink pen embodiments, the vacuum port comprises a vacuum chamber surrounding the discharge port. The charge despositing styli in the electrographic printing embodiment are also surrounded by the vacuum chamber.

15 Claims, 10 Drawing Figures APPARATUS FOR AND METHOD OF GRAIIIICAL RECORDING WITH SIMULTANEOUS CHARGING AND INKING BACKGROUND OF THE INVENTION This invention relates to graphical recording with an ink pen system or an electrostatic system such as an electrographic marking system.

In electrographic recording, charge patterns are deposited on dielectric coated paper for subsequent development of the charge image with oppositely charged toner particles of a dry powder or colloidal suspension in an electrically insulating liquid. When the charge sites on the paper are brought into contact with the toner as the paper passes through the toner tank, the charged toner particles begin to move toward the charge sites under the influence of the field established by the deposited charge. Where negative charges are deposited on the paper, positive toner particles will be attracted to the negative charges at the various charge sites. When this juxtaposition of charged paper and charged toner particles is allowed to remain for a time, enough toner particles migrate through the toner liquid to the charge sites to neutralize the deposited charges and thereby cancel the surface potential associated with them. When this happens, the record image is said to be fully toned.

One very important form of electrostatic recording is electrographic printing wherein it is desirable to have the-toned image visible promptly after the charge has been deposited. The factor which determines the delay time between charge deposition and the viewing of the record in electrographic printing is the transit time during the toning process.

In the conventional electrographic printing apparatus, charges are first deposited on dielectric coated paper which is then driven through the lower portion ofa tank containingliquid toner which wets the surface of the paper. In many cases, the paper then passes above the toner level in the tank where it is subjected to a vacuum which removes the excess toner liquid from the surface of the paper so that a nearly dry image emerges from the toner tan'kfor viewing.

In a system of this type, the paper with its deposited charges is moving relative. to the toner liquid. During the period of contact between the charged paper and the. toner, only those toner particles which happen to be within some minimum distance of the charged surface can be trapped to effect toning. Toner particles farther from the charged surface than this minimum distance do not have sufficient time to move through the toner liquid to be trapped before the charge site attracting them has moved too far away for its field to be effective. Because only those toner particles closeto the charged surface can effect toning quickly, a relatively long residence time in the toner tank is necessary.

to fully tone the paper. Consequently, the transit time through the toner tank after the charge has been deposited on the paper before entry into the toner tank results in a relatively long imaging delay. Although the imaging delay is not particularly significant where the paper record is moving rapidly through the toner tank, it can become very significant when the paper record moves slowly through the toner tank. 3

In theelectrographic recording system shown in U.S. Pat. No. 3,342,164 Lewis, liquid toner is circulated between an inlet and an outlet of an elongated developer compartment (toner chamber) which extends transversely across the path of a record carrying previously deposited charges so as to move relatively large quantities of toner across the record. In order to re move any excess toner from the record, elongated vacuum ports extend transversely across the path of the record on either side of the toner chamber. Thus the principal flow of toner is from the inlet which is at atmospheric pressure to the outlet of the toner chamber rather than to the elongated vacuum ports which merely remove the excess toner. The toner is confined by the walls of the toner chamber, not by any pressure differential between the inlet and the outlet from the toner chamber.

Although some increase in the speed of electrographic printing may be realized by the system disclosed in the Lewis patent, the layers of toner immediately adjacent the record move rather slowly just as the water adjacent a river bed moves rather slowly. This delays inspection of the record since the record must move slowly enough to attract charged tonerparticles remote from the record as well as the slow moving particles at the record. Also, deposition of the latent charge image before moving the record through the toner chamber further delays inspection of the record. A somewhat similar system is shown in U.S. Pat. no. 3,401,393 Cirimele et al.

In conventional ink pen systems used for graphical recording, a pen traverses a record receiving medium such as ordinary chart paper for depositing ink to form a record. Pen systems used for this purpose include ball point pens and various types of capillary feed pens some of which have employed a pressurized ink supply to augment ink flow for high speed writing. In addition to the usual problems of clogging, bleeding, tearing chart paper and the like, increased writing speeds result in skipping caused by pen bounce and by inadequate ink flow. To date, attempts to solve these problems have included the use of special inks, specially designed feed reservoirs, and pressurized ink systems which are often pressure modulated as a function of pen speed. Attempts to provide adequate ink flow for high speed writing without having excessive ink flow for'low'sp'eed writing or with the pen stopped have been complicated and expensive.

SUMMARY OF THE INVENTION In accordance with one aspect of the invention, apparatus is provided for producing visible marks on a record receiving medium comprising reservoir means containing a marking liquid, a discharge port for applying marking liquid from the reservoir means to' a record receiving medium and a vacuum port in substantial communication with the discharge port. Means are also provided for establishing a substantial vacuum at the vacuum port and substantial pressure at the discharge port to force the marking liquid through the discharge port and into the vacuum port thereby establishing a substantially continuous flow of marking liquid.

In accordance with another aspect of the invention, a sufficient vacuum is established at the vacuum port so as to substantially confine the flow of marking liquid over the record receiving medium to the area between the discharge port and the vacuum port.

'In one preferred embodiment of the invention, an electrostatic recording apparatus is provided wherein the marking liquid comprises a toner. High velocity flow of a thin toner liquid layer is established between the discharge port and the vacuum port with the velocity of the liquid toner flow exceeding the rate of movement between the record receiving medium and the discharge port. In accordance with another aspect of the invention, the vacuum port comprises a vacuum chamber which substantially surrounds the discharge port. In accordance with another aspect of the invention, the flow between the discharge port and the vacuum port includes a substantial component of flow parallel with the relative movement between the record receiving medium and the discharge port. At least one charge depositing stylus for electrostatic recording is located within the liquid toner flow path from the discharge port.

BRIEF DESCRIPTION OF THE DRAWINGS These and other aspects of the invention may be understood from the following description taken in conjunction with the following drawings in which:

FIG. 1 is a perspective view of a partially sectioned eleetrographic imaging head constructed in accordance with the invention;

FIG. 2 is an enlarged cross-sectional view of the head shown in FIG. 1;

FIG. 3 illustrates another electrographic imaging head and its associated electrographic toner circulation system;

FIG. 4 illustrates another electrographic imaging head constructed in accordance with this invention so as to have an electrographic stylus array within the head;

FIG. 5 is a perspective view of yet another electrographic printing head constructed in accordance with this invention and having a stylus array located within the head;

FIG. 6 is a cross-sectional view of an electrographic pen constructed in accordance with this invention;

FIG. 7, consisting of FIGS. 7a to 7c, illustrates various single and multiple electrographic pen arrays; and

FIG. 8 is a sectional view of an ink pen embodiment of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS FIG. 1 illustrates an improved electrographic imaging head configuration which overcomes the transit time limitations of prior art devices. On one surface of a block 10 which forms the imaging head, a toner discharge port 11 is provided, shown here as a long narrow slot. The toner discharge port 11 is supplied toner through a toner input port and passage13 which is connected to a suitable reservoir of toner maintained under positive pressure. Surrounding the toner discharge port 11 is a vacuum port comprising a suction moat or chamber 12 connected through a vacuum passage 14 to a suitable vacuum source.

FIG. 2 shows a sectional view of the imaging head configuration of FIG. 1 in which like features are indicated by like numbers. Also shown in FIG. 2 is a segment of a moving chart 15 which is to be toned. Note that the head is spaced a small distance from the chart 15 shown exaggerated here for descriptive clarity.

The operation of the imaging head configuration is as follows: Toner liquid entering the input port and passage 13 under positive pressure passes to the toner discharge port 11. The toner flows from the port 11 in a thin, high velocity layer over the latent charge image which has been deposited on the moving ch'art 15 with the velocity of the toner exceeding the relative velocity between the discharge port 11 and the chartlS. The toner is then collected in the chamber 12 and withdrawn through the chamber 12 and passage 14. Reduced pressure to the vacuum chamber 12 also serves to confine the toner to an area between the discharge port 11 and the chamber 12 and remove excess toner liquid from the paper surface to produce a dry record.

The high velocity of toner liquid (approximately l0-l00 in./sec.) relative to the charged paper surface has the effect of producing substantial relative motion between the supply of toner particles and the coated paper surface of the chart 15 thereby accomplishing the same result as is obtained with the long contact time employed in prior art systems. Because adequate toning can now be accomplished over a relatively short distance, the transit time at low chart speeds is correspondingly reduced compared to the prior art practice.

The planar imaging head surface, shown in FIGS. 1 and 2, may have other forms as will now be described with reference to FIG. 3. In the embodiment of FIG. 3, a curved imaging head 10 is incorporated. into an electrographic recording system having a suitable chart feed arrangement, charging stylus array and an associated continuous liquid toner circulation system. Again, the features corresponding to those shown in earlier figures carry similar reference characters.

The chart paper 15 is shown passing from a feed roll 16, over a stylus array 17 and around a backing roller 18 to a takeup roller 19. The imaging head 10 with its curved head surface is adapted to fit closely around the paper 15 as it passes over the backing roller 18. Note that substantially all of the toner fluid flow is parallel with the movement of the paper 15. Toning of the latent charge image produced by the stylus array 17 is initiated by starting up a pump20.

The pump 20 reduces pressure in the vacuum chamber 12. Air entering by leakage into the vacuum chamber 12 and inwardly through a suction relief valve 21 is pumped via a vacuum line 22 into an air space 23 at the top of a toner reservoir 24 thereby increasing the internal pressure of the reservoir. This pressure head drives toner fluid out of the bottom of the reservoir 24 via a feed line 25 through a solenoid valve 26 and into the toner inlet port and passage 13. The resulting flow is then collected in a supply manifold 27 which distributes toner uniformly to the toner discharge port 11.

The removal of excess toner fluid in the vacuum chamber 12 nowproduces a mixture of air and toner fluid pumped into the air space 23 of the reservoir 24 where the mixture is separated.

A pressure relief valve 28 prevents excessive air pressure build-up during continuous operation. For proper shut-down of the imaging system, the solenoid valve 26 in the toner feed line 25 vents a line 29 to the air space 23 of the toner reservoir 24. With the toner feed thus interrupted, the pump 20 is allowed to remain running for a short period in order to purge the imaging head of any remaining fluid. It should be noted that in the event of a loss of chart paper due to a break, or the end of a supply of chart paper, no spillage will occur and the shut-down procedure still applies. Also, because toner fluid is supplied to the toner discharge port 11 under pressure, uniform toning over the full width of the chart is maintained even though an instrument incorporating this imaging system might be tilted from its normal operating position. I

In the embodiment shown in FIG. 3, the stylus array 17 is physically separated from the imaging head. In the embodiment of FIG. 4, the stylus array is located within the imaging head and in the toner flow path so as to provide the functions of charge deposition and imaging in a compact structure in order to further reduce the imaging delays inherent in electrographic printing.

The imaging head in the embodiment of FIG. 4 comprises two-mating blocks a and 10b with a marking stylus array 17 assembled between the two blocks 10a and 10b. The stylus array 17 is shown as fabricated on a PC board 17a as an etched stylus array 17 having leads 30 for making external electrical connections. The stylus assembly is arranged so as to come in close proximity with the paper for charge deposition.

Also shown in FIG. 4 are the toner discharge port 11 with its associated toner supply manifold 27 and the vacuum chamber 12 positioned in close proximity with the chart paper 15. While it is well known that a charged electrode in contact with a toner fluid having oppositely charged particles will attract the toner particles to the electrode, it has been found in practice that only a thin layer of toner particles will adhere and that this does not, in fact,v prevent the desired electrographic marking.

In the embodiment of FIG. 5, a stylus array 17 is encased in an insulating material adjacent the toner discharge port 11. Both the stylus array 17 and the discharge port 11 are then surrounded by the vacuum chamber 12. The chamber 12 is then connected to the vacuum passages 14 through small openings in the chamber 12 located on opposite sides of the stylus array 17 and the discharge port 11. The toner is supplied to the discharge port 11 through a hollow tube forming the toner inlet passage 13. Each stylus in the array 17 is individually connected to one of a plurality of electrical leads 30 so as to permit each stylus to be selectively energized. Note that the deposition of a charge by the selective energization of the styli in the array 17 occurs while toner is simultaneously applied to the charge site because the entire volume surrounded by the chamber 12 and between the paper and the inner surface 12a of the head is filled with toner fluid. Thus, there is no delay between the time that the charge is deposited on the paper and the time that the toner is applied to the charge sites.

FIG. 6 shows an electrographic pen suitable for producing a continuous trace record as in conventional XT or XY recording. A pen tube 31 is connected by means of a conductor 32 to a suitable high voltage for continuous deposition of charge on a recording chart 15. Pen tube 31 has its inner passage connected to a supply of toner liquid under suitable positive pressure for delivering toner through a terminal discharge port 11 to the charge sites while simultaneously depositing the charge through the tube 31 itself. The tip of the tube 31 may advantageously be made uneven soas to provide a passage for the flow of toner liquid between the pen tip at the'discharge port 11 and the paper while maintaining close proximity'between the pen tip and the paper for ease of charge deposition. I

Surrounding the pen tube 31 is a suction sleeve-33 spaced a small distance away from the chart paper 15. The suction sleeve 33 provides a vacuum port 12 and a connection 34 to a suitable vacuum source not shown.

In operation, as the pen assembly is moved along the paper, the charge trace laid down by the pen tip is continuously and simultaneously toned by the toner fluid flowing under pressure outwardly from the pen tip in a thin, high velocity film as previously described. The outward flow of toner fluid is drawn up by a vacuum leaving the resultant visible trace dry as previously described. The high voltage supply to the tube 31 through the lead 32 may be interrupted in a controlled manner to identify one trace in the presence of others as in multiple pen recorders.

In FIG. 7a, the pen tube 31 and the suction tube 33 of the pen shown in FIG. 6 are illustrated. In FIG. 7b, the pen tube 31 has been replaced by an array of pen tubes 35 having elongated openings in an arrangement suitable for a 7-bar segment numeric display. In a like manner, FIG. 7c shown the single pen tube 31 replaced by a 5X7 pen tube matrix 36 suitable for producing alpha numeric displays. These pen arrays may be used either to draw continuous or interrupted single pen traces or to produce trace identifying numeric or alpha numeric characters such as may be desired from multipoint recordings. As an alternative structure the matrix elements may be solid conductors with the interstices providing multiple flow paths for toner fluid surrounded by a single pen tube.'Such a multi-electrode marking array would be surrounded by a suction sleeve as previously described.

A further useful form of array of the type shown in FIG. 7b and 7c is one in which the pen tubes are arranged in-line as are the styli shown in FIG. 5. Such an array would fulfill the objectives set forth in connection with FIGS. 4 and 5 wherein the marking styli are incorporated into printing heads for achieving minimum transit delay.

A structure similar to that shown in FIG. 6 may be used as a conventional ink pen but without conductor 32 connected to pen tube 31 which is capable of very slow writing speeds without clogging, bleeding or tearing-chart paper while also being capable of very high writing speeds with a variety of inks without skipping. The operation of the pen with ink is substantially the same as the operation with toner fluid, i.e., the pen tube 31 is coupled to a suitable source of ink under pressure for delivering ink to the writing surface at a flow rate sufficient for the highest writing speed intended and the suction or vacuum sleeve 33 is connected to a suitable source of suction for removing any excess ink from the printing surface when writing at speeds lower than the maximum. Pens constructed and operated according to this invention have been capable of writing at high speed and then of being brought to rest indefinitely without bleeding or displayingother undesirable characteristics. Furthermore, demonstrations have shown that such pens can write under conditions of low chart speed and much retracing without clogging or-bleeding. These desirable performance capabilities have been achieved with inks having a broad range of characteristics.

FIG. 8 shows another ink pen embodiment having features which make it preferable for use under-conditions where continued retracing is expected. The pen tube 31 and the suction sleeve 33 are shown with a spacer 37 added for positioning the pen structure accurately a short distance from the writingsurface'. In this cmbodiment, the ends of the pen tube 3] and the suction sleeve 33 are made more or less coplanar. Because the pen tube 31 is now separated from the writing surface rather than in contact with it, the suction in the suction sleeve now serves both to draw up excess ink delivered to the writing surface and to draw ink outwardly through the pen tube. Furthermore, because the pen tube does not touch the paper it cannot abrade the paper while it is wet by the ink. Spacer member 37 may be located so that it touches the writing surface only at a spot which has not yet been wet by ink. When a pen of this design is lifted off the writing surface, the suction no longer serves to draw ink through the pen tube and ink delivery is thus automatically stopped. When the spacer is on the writing surface, the pen produces a fountain of ink in contact with the writing surface. The suction or vacuum produced by the suction sleeve 33 evacuates the chamber at a periphery of the area being contacted by the ink so as to confine the ink to a limited area.

in some applications, it may be important to have the pen tip visible so that the record may be viewed continuously as it is made. For this purpose, the suction sleeve may be made of a transparent material. To maintain visibility through the suction sleeve, it may be made from or coated internally with a material which is not wettable by the ink being used. When desired, the spacer foot 37 may be made adjustable so that the vacuum may be varied thereby varying the rate of ink flow through the pen tube. When used to write on a curved surface such as a recorder drive roll, the end of the suction sleeve may be curved to conform to the writing surface shape.

Both in the description of the various eleetrographic marking embodiments and in the ink pen embodiments of this invention, the marking fluid was either described as, or tacitly assumed to be continuously recirculating. in many applications, the marking fluid need not be recirculated continuously, but may instead be supplied from a supply reservoir during a recording period and then replenished before the next recording period. For very high writing speeds and recording period may be only a few seconds. The excess marking fluid drawn off by the suction moat or suction sleeve may be collected in a reservoir and periodicallyreturned to the supply reservoir or it may be desirable to consider the collected excess marking fluid as spent, and discard it. When the collected excess marking fluid is to be returned to the supply reservoir for reuse, the means for effecting the transfer may take many forms. In the most simple means, the two reservoirs are made physically identical so that they may be interchanged as needed to effect the required transfer. A, next further degree of complication and attendant convenience could be a simple manually or solenoid operated plunger type pump for transferring marking fluid from the collection to the supply reservoir. Yet another means may be implemented with a suction pump having a pressure connection available at its discharge so that a single pump may be used both to provide suction and to provide a source of driving pressure whereby the same source of suction and pressure used in normal operation may be valved as desired to effect periodic marking fluid transfer. Alternatively, a suction only pump may be used to provide suction for normal operation and for effecting fluid transfer. When this is done, the marking fluid drive pressure may be obtained from stored energy in a spring or mass loaded devicc acting on a flexible diaphragm or on a collapsible supply reservoir.

It will be understood further, with regard to the electrostatic systems described, that other charge pattern generating means may be utilized including electrophotographic means which are well known in the art.

The invention may be utilized in conjunction with a helical drum recorder such as that shown in U.S. Pat. No. 2,560,256 Shrader. In such an embodiment, an elongated electrode extending parallel with the axis of the helical drum would be located in the flow path of the toner liquid. By energizing the electrode at the appropriate time, an electrostatic charge would be applied in the appropriate position on a dielectric strip chart. The electrostatic charge would then be toned by the toner liquid.

These and other modifications may be made without departing from the spirit and scope of the invention as set forth in the appended claims.

What is claimed is:

1. An electrostatic recording apparatus for applying liquid toner to a record receiving medium on which a latent electrostatic record is being applied comprising a reservoir means containing said liquid toner;

a discharge port for said reservoir means for forming a discharge path of said liquid toner over said record receiving medium; and

a stylus for applying said latent electrostatic record to said record receiving medium, said stylus being located within the liquid toner flow path over said record receiving medium from said discharge port.

2. The apparatus of claim 1 further comprising a vacuum port adjacent said discharge port, said toner flow path extending from said discharge port to said vacuum port.

3. The apparatus of claim 2 wherein said vacuum port comprises a chamber surrounding said discharge port.

4. The apparatus of claim 3 wherein said stylus is a tubular member having an opening forming said discharge port.

5. The apparatus of claim 3 including a plurality of styli forminga stylus array wherein each stylus comprises a tubular member having an opening forming a discharge port.

6. A method of electrostatic recording comprising the steps of:

directing a toner liquid toward a record receiving medium;

contacting said record receiving medium in a specifled area with said toner liquid; and simultaneously applying an electrostatic charge to said specified area during said contacting.

7. The method of claim 6 further comprising the step of evacuating said toner liquid from said specified area.

8. The method of claim 7 further comprising the step of evacuating said toner liquid along the edges of said specified area.

9. An electrostatic recording apparatus for applying liquid toner to a record medium on which a latent electrostatic record is applied comprising:

a reservoir means containing said liquid toner, said.

reservoir means having a discharge port adjacent said record medium for applying said liquid toner to said record medium;

vacuum means having a vacuum port adjacent said record medium and said discharge port of said reservoir means for creating a liquid toner discharge path over said record medium from said discharge port to said vacuum port; and

a charge deposition electrode located adjacent said recording medium and in the flow path between said vacuum port and said discharge port for applying a latent electrostatic record to said record receiving medium.

10. The electrostatic recording apparatus of claim 9 comprising a recording head carrying said discharge port, said vacuum port and said electrode thereon.

11. The electrostatic recording apparatus of claim 10 wherein said vacuum port substantially surrounds said electrode and said discharge port.

UNtIiTED STATES PATENT OFFICE CERTIFICATE OF CORRECTION V "l3 7 93,638 Dated February 19, 1974 Edward L. Weiss et a1.

Patent No.

Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Delete ail drawings as printed as substitute the attached drawings.

' Y si ned and sealed this 14th day'of January 1975.

(SEAL) Attestaf McCOY M. GIBSON JR. c. MARSHALL DANN Attesting Officer Commissioner of Patents USCOMM-DC 603764 69 F ORM PO-1050 (10-69) u.s, GOVERNMENT nmnma orncz; 930

Patent No. 3,793,638

February 19, 1974 Page: 3 

1. An electrostatic recording apparatus for applying liquid toner to a record receiving medium on which a latent electrostatic record is being applied comprising a reservoir means containing said liquid toner; a discharge port for said reservoir means for forming a discharge path of said liquid toner over said record receiving medium; and a stylus for applying said latent electrostatic record to said record receiving medium, said stylus being located within the liquid toner flow path over said record receiving medium from said discharge port.
 2. The apparatus of claim 1 further comprising a vacuum port adjacent said discharge port, said toner flow path extending from said discharge port to said vacuum port.
 3. The apparatus of claim 2 wherein said vacuum port comprises a chamber surrounding said discharge port.
 4. The apparatus of claim 3 wherein said stylus is a tubular member having an opening forming said discharge port.
 5. The apparatus of claim 3 including a plurality of styli forming a stylus array wherein each stylus comprises a tubular member having an opening forming a discharge port.
 6. A method of electrostatic recording comprising the steps of: directing a toner liquid toward a record receiving medium; contacting said record receiving medium in a specified area with said toner liquid; and simultaneously applying an electrostatic charge to said specified area during said contacting.
 7. The method of claim 6 further comprising the step of evacuating said toner liquid from said specified area.
 8. The method of claim 7 further comprising the step of evacuating said toner liquid along the edges of said specified area.
 9. An electrostatic recording apparatus for applying liquid toner to a record medium on which a latent electrostatic record is applied comprising: a reservoir means containing said liquid tOner, said reservoir means having a discharge port adjacent said record medium for applying said liquid toner to said record medium; vacuum means having a vacuum port adjacent said record medium and said discharge port of said reservoir means for creating a liquid toner discharge path over said record medium from said discharge port to said vacuum port; and a charge deposition electrode located adjacent said recording medium and in the flow path between said vacuum port and said discharge port for applying a latent electrostatic record to said record receiving medium.
 10. The electrostatic recording apparatus of claim 9 comprising a recording head carrying said discharge port, said vacuum port and said electrode thereon.
 11. The electrostatic recording apparatus of claim 10 wherein said vacuum port substantially surrounds said electrode and said discharge port.
 12. The electrostatic recording apparatus of claim 11 wherein said electrode is spaced from said discharge port and said vacuum port.
 13. The electrostatic recording apparatus of claim 12 comprising more than one said electrode arranged in an array.
 14. The electrostatic recording apparatus of claim 11 wherein said electrode comprises a tube having a central opening forming said discharge port.
 15. The electrostatic recording apparatus of claim 14 comprising more than one said tube arranged in an array. 